Rocket propulsion method



July 28, 1959 A. ZLETZ ETAI. 2,896,407

ROCKET PROPULSION METHOD Filed Feb. 16. 1953 OP 4 I3 I /6 OX/DIZER INVENTORS: Alex Z/ef:

Q00 R. rmqdy ATTORNEY United States Patent 2,896,407 ROCKET PROPUISION METHOD Alex Zletz, Park Forest, and Don R. Carmody, Crete, 111., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana Application February 16, 1953, Serial No. 336,910 20 Claims- (Cl. 60-354) This invention relates to the generation of gas. More particularly, it relates to reaction propulsion by the hypergolic reaction of a liquid fuel and a liquid oxidizer. Still more particularly, the invention relates to a method of rocket propulsion by the hypergolic reaction of a fuel and a hydrogen peroxide oxidizer, which materials spontaneously react to generate gas at high pressure and high temperature. I

Reaction propulsion is now being used for many aerial purposes. For many uses it is necessary to operate with a fuel system which is not dependent on atmospheric oxygen. This fuel system may consist of a single selfcontained propellant or it may consist of a separate fuel and a separate oxidizer, i.e., a bipropellant system.

In the bipropellant system the fuel and the oxidizer are introduced separately and essentially simultaneously into the combustion chamber of the reaction motor. The products of oxidation from the reaction of the fuel and the oxidizer are discharged through an orifice at the exit end of the combustion chamber and thereby produce the driving force. Because of the possibilities of electrical and/or mechanical failure of the auxiliary methods of ignition such as a spark or a hot surface, it is preferred to use a self-igniting fuel system. A fuel which is selfigniting, i.e., spontaneously combustible when contacted with an oxidizer, is known as a hypergolic fuel.

Temperature has an important effect on the hypergolic activity of fuels. The temperature at the earths surface may vary from a high of about +125 F. to a low of as much as 65 F.; in general temperatures below about -20 or 30 F. are exceptional. Thus surfaceto-air missiles or rocket-driven aircraft should be capable of operation when the temperature of the fuel and the oxidizer at the moment of initial contact in the com- ,bustion chamber of the rocket motor is on the order of -20 F. Temperatures at high altitudes are frequently on the order of 65 F. and are known to approach -l00 F. Thus an air-to-air missile should be able to operate satisfactorily when the temperature of the fuel and the oxidizer at the moment of initial contacting in the combustion chamber is on the order of 65 F.

The more common oxidizers are white fuming nitric acid, red fuming nitric acid and nitric acid-sulfuric acid mixtures. While these nitric acid oxidizers operate satisfactorily over a wide range of atmospheric temperatures they have important drawbacks. The nitric acid oxidizers are extremely corrosive; they have poor storage stability;

they give off toxic gases; and special precautions must be taken by personnel who handle these oxidizers.

Concentrated aqueous hydrogen peroxide solutions have excellent storage stability and do not give off harmful gas. However, these aqueous hydrogen peroxide solutions such as 90% hydrogen peroxide have the disadvantage of comparatively high freezing points, e.g., 90% hydrogen peroxide solution freezes at +l2 F. The freezing point of 80% hydrogenperoxide is 9 F., but

' the activity of this solution toward the prior art fuels is markedly lower than the 90% H 0 solution. The freez- "ice ' ing point of aqueous hydrogen peroxide solutions can be depressed by dissolving therein inorganic salts, preferably ammonium nitrate. Thus a solution containing 40 weight percent of ammonium nitrate and in which the hydrogen peroxide-water portion contains 90 weight percent of H 0 has a freezing point of about 30 F. A so-called 80% H,O,30% NH NO solution has a freezing point of below 70 F.

Concentrated aqueous hydrogen peroxide solutions have been used as monopropellants by catalytically decomposing the hydrogen peroxide using such catalysts as potassium permanganate or copper oxide. Since the decomposition products contain free-oxygen the monopropellant system is ineflicient. However, fuels which are hypergolic with nitric acid oxidizers may be much less active or even inactive with concentrated H O, solutions. Anhydrous hydrazine is usually considered to he the only fuel that is sufficiently hypergolic with concentrated H 0 solutions to "be practical; however, hydrazine has the disability of a comparatively high freezing point.

' Some fuels are operative with H O, solutions in the presence of an H O; decomposition catalyst. Furthermore, the prior art fuels are less effective with ammonium nitrate containing aqueous hydrogen peroxide than with aqueous hydrogen peroxide alone.

An object of this invention is a method of generating gas by the hypergolic reaction of a fuel and a hydrogen peroxide oxidizer. Another object is a method of reaction propulsion by the hypergolic interaction of a fuel and a hydrogen peroxide oxidizer. Still another object is a method of reaction propulsion by the hypergolic intgaction of a hydrogen peroxide oxidizer and a fuel which contains appreciable amounts of hydrocarbons, particularly non-hypergolic liquid hydrocarbons. A particular object is a method of generating gas by the hypergolic interaction of a defined fuel and an oxidizer consisting of an aqueous hydrogen peroxide solution containing dissolved ammonium nitrate. Another particular object is a method of rocket propulsion by the hypergolic interaction of a defined organic halothioborate and a defined hydrogen peroxide oxidizer when the temperature of the fuel and the oxidizer is above about 70 F.

Other objects will become apparent in the course of the detailed description of the invention.

A method has been discovered which gas may be used as a substitute for compressed air for certain purposes or for driving the turbine of a jet engine or for rocket propulsion, which method comone aliphatic radical and wherein the halogen radical is selected from the class consisting of chlorine and bromine, and

(2) An oxidizer selected from the class consisting of (a) Aqueous hydrogen peroxide solutions which contain at least about weight percent of H 0 and the remainder is essentially water and (b) Aqueous hydrogen peroxide-inorganic salt solutions wherein the hydrogen peroxide water portion contains at least about 80 weight percent of H 0 A mixed fuel made up of methylhalothioborate which contains as much as 50 volume percent of miscible hydrocarbon is hypergolic with aqueous hydrogen peroxideammonium nitrate solutions containing at least about weight percent of hydrogen peroxide in the H O -water for generating gas,

portion when the fuel and the oxidizer are at a temperature of about F. The lower the temperature of initial contact the less hydrocarbon tolerable in the muted fuel.

Certain organic halothioborates ignite spontaneously when contacted with hydrogen peroxide oxidizers." The various halothioborates do not have equal hypergolic activity with the same oxidizer. However, by proper selection of the halothioborate, it is possible to obtain a hypergolic reaction with a tolerable ignition delay when the halothioborate and the oxidizer are at a temperature of about -70 F. at the moment of initial contact in the gas generating chamber.

These organic halothioborates have the generic empirical formula (RS),,BX,, where B represents the element boron, S represents the element sulfur, X represents a v halogen radical selected from the class consisting of chlorine and bromine, and R represents an aliphatic hydrocarbon radical, and wherein e" is l or 2, "g" is 1 or 2 and the sum of e and "g" is 3.

The halothioborates which are suitable for the purposes of this invention contain aliphatic hydrocarbon radicals which may be paraflinic, e.g., methyl, ethyl, isopropyl and n-propyl; or olefinic, e.g., ethenyl, propenyl, isopropenyl, or acetylenic, e.g. ethinyl and propinyl; or cycloalkyl and cycloalkenyl, e.g., cyclopropyl and cyclopropenyl. In the case of the aliphatic-dihalothioborates, the total number of carbon atoms should be not more than 8; while in the case of the dialiphatichalothioborates, the total number of carbon atoms should be not more than 12 and not more than 8 carbon atoms should be present in any one aliphatic radical.

The most suitable halothioborates for the purposes of this invention are the alkylhalothioborates wherein the alkyl radicals are selected from the group consisting of methyl, ethyl and mixtures thereof. For operation where the halothioborate and the oxidizer will be at a temperature of about --70 F. at the moment of initial contacting of the halothioborate and the oxidizer, the preferred halothioborates are the methylhalothioborates.

A mixed fuel which is suitable for the generation of gas can be made by mixing aliphatichalothioborates with miscible hydrocarbons. The minimum amount of halothioborate necessarily present in said hypergolic mixed fuel will vary with the type of hydrocarbon, the desired temperature of operation and the type of H 0 oxidizer. For example: As much as 50% of a petroleum fraction is tolerable in a hydrocarbondimethylchlorodithioborate blend which is hypergolic at about +60 F. when using an ammonium nitrate containing 90% hydrogen peroxide oxidizer. In general petroleum hydrocarbon fractions are suitable materials as for example those fractions boiling between about 300 and 600 F. which correspond to the fuel requirement of military jet engines. Aromatic hydrocarbons which boil below about 600 F. are suitable hydrocarbons for this purpose. The hypergolic activity of the mixed fuel can be improved at lower atmospheric temperatures by using as the hydrocarbon component olefinic hydrocarbons such as thermally cracked naphthas and gas oils or turpentine. Conversely, at higher atmospheric temperatures a hypergolic mixed fuel containing less halothioborate is obtainable by the use of unsaturated hydrocarbons.

The oxidizers of this invention are either concentrated aqueous hydrogen peroxide solutions or aqueous hydrogen peroxide solutions containing dissolved inorganic salts, for example, ammonium halides, sodium sulfate, sodium nitrate, etc.; for low temperature operation requiring a short ignition delay, ammonium nitrate must be used as the salt. The concentrated aqueous hydrogen peroxide solutions should contain at least about 80 weight percent of H 0 the remainder of the solution is essentially water.

Thehypergolic activity of the aqueous hydrogen peroxide solution is improved by increasing the concentra- 4 tion of the peroxide. Commercially available 90% H 0 solution is an excellent oxidizer for operation above 0 F. For low temperature operation it is preferred to use aqueous H m-ammonium nitrate solutions, such as 90%- 40%" or 80%--30%" solutions.

Concentrated aqueous hydrogen peroxide solution as made commercially is virtually only H 0 and water.

V In order to improve storage stability small amounts of stabilizers arecomrnonly added to the solution, e.g., so dium stannate, tetrasodium pyrophosphate, adipic acid, tartaric acid; in general only trace amounts of stabilizers are added so that the solution consists essentially of hydrogen peroxide and water.

In order to depress the freezing point of aqueous hydrogen peroxide solutions soluble inorganic salts are dissolved therein, eg. sodium nitrate, potassium nitrate and ammonium nitrate have been used. These salt-containing solutions are commonly designated in terms of the weight percent of salt in the total solution and the weight percent of hydrogen peroxide present in the aqueous portion of the solution, e.g., H O 40% NH N0 indicates that the total aqueous hydrogen peroxide-nitrate solution consists of 40 weight percent of ammonium nitrate and 60 weight percent of aqueous hydrogen peroxide composed of 90 weight percent of H 0, and the remainder essentially water. This particular solution has a freezing point of 30 F. A temperature of -70 F. is attainable with an 80% H20r-30% NH N0 solution. It is preferred to operate in the presence of ammonium nitrate because of the pronounced favorable effect on the hypergolic activity of the fuels of this invention.

It has previously been found that trithioborates having the empirical formula RR'R"S B where R, R and R" represent aliphatic hydrocarbon radicals containing from 1 to 3 carbon atoms and the total number of carbon atoms in the molecule between 3 and 7 are hypergolic with the above defined H 0 oxidizers at temperatures above about -20 F. Examples of these fuels are trimethyltrithioborate and triethyltrithioborate. The hypergolic activity of these fuels at lower temperatures can be greatly irnproved by adding thereto small amounts of the above defined halothioborates, i.e., the halothioborates have a synergistic catalytic effect on the activity of the aliphaticthioborates. For low temperatures the halothioboratethioborate fuel should contain between about 0.5 and 20 volume percent of the halothioborate.

Dimethylchlorodithioborate was prepared as follows: Boron trichloride was introduced into a 3-necked flask, which contained methyl mercaptan in the approximate ration of 3 mols of mercaptan per mol of boron trichloride, and was provided with a Dry-Ice condenser. After the addition of boron trichloride over a period of 3 hours at reflux temperature the reaction mixture was maintained at reflux temperature (about 10 C. for 4 /2 hours). The cooler was removed from the flask and the flask permitted to reach room temperature while stirring. The pressure in the flask was progressively decreased by withdrawing gaseous materials therefrom, ambient temperature being maintained for the fractionation process. Two overhead fractions were obtained. The first boiled from about mm. to 1 mm. of Hg. The second boiled below 1 mm. of Hg pressure. The second fraction analyzed 25.9 wt. percent chlorine-the theoretical chlorine content of (CH S) BCl is 25.2 wt. percent. The dimethyl chlorodithioborate was fluid and free-flowing at Dry-Ice temperature.

The ignition characteristics of various fuels were studied using a drop test. This method utilizes a test tube, 1 in. x 4 in., containing about 0.5 ml. of oxidizer. The fuel to be tested was drawn into a hypodermic syringe. It was then ejected forcibly against the oxidizer surface by depressing the syringe plunger. By this method amounts of fuel of as little as 0.01 ml. can be added. Low temperature tests were carried out by cooland the oxidizer contained therein by a drying tube inserted into the top of The fuel was cooled By supercooling the test tube means of a bath; the test tube excluded moisture. separately to the desired test temperature.

ing it was possible to carry out tests at temperatures below the freezing point of the fuel and/or the oxidizer.

The "ignition delay, which is the time elapsing between the addition of fuel to the oxidizer and visual ignition thereof, was determined as either (a) very short N t l ffi Tem Ignition a e r rp ml. NHrNOa, F. delay percent 0. 10 80-30 50 1 sec. 0. 10 80-30 60 12 sec. 0. 16 80-30 60 1 sec 0. 15 80-30 -70 18 sec. 0. 18 80-30 70 1 see Test 11 For comparative purposes hydrazine was contacted at various temperatures with various H 0 solutions as the oxidizer.

Bun B 0 Fuel Temp.

N o. oxidiz r, added, F. Ignition delay percent ml.

6. 90 0. 05 +70 Very short. 7 80 0. 03 +70 Short. i 80 0.10 +14 No ignition (eflervescence).

90-40 0. 03 +14 No ignition. h 90 0. 03 +14 Very short.

Test 111 The hypergolic activity of a mixture of thioborate and halothioborate was tested. Triethyltrithioborate prepared by reacting B01 and ethyl mercaptan was fractionated under conditions such that a trace amount of chlorine remained therein; believed to be diethylchlorodithioborate. The activity of this mixture was compared with chlorine-free triethyltrithioborate.

1am H10, Fuel Temp. No. Fuel oxidizer, added, F. Ignition delay percent ml.

10.--... Mixed.--. 90 0.06 +70 Short. 11...-.- Pu1'e".... 90 0.06 +70 No ignition. do 90 0. 09 +70 11 sec.

These runsshow the favorable effect on ignition delay of a trace amount of the halo derivative on the activity of the trithioborate.

It is obvious from the data presented above that this invention can be used to generate gas at high pressure. This gas can be used for operating mac ery such as compressed air hammers" or for aircraft catapults; another important use for this high pressure gas is in the starting of the turbines of jet-type engines. The invention is particularly useful in aerial missiles which require a compact power plant that develops large amounts of which corresponds to substantially less energy over a very short period of time. Other examples of the use of this invention are: the rocket-assisted takeofl or flight of aircraft; aerial missiles; boosters for surface vehicles.

The relative'proportion of oxidizer-tofuel used will depend upon the type of operation, the temperature of operation and the type of fuel and oxidizer being used. When using a %.40% hydrogen peroxide-ammonium nitrate solution as the oxidizer and dimethylchlorodithioborate as the fuel, between about 4 and 5 volumes of oxidizer are needed per volume of fuel..-

By way of example this invention is'applied to the propulsion of a surface-to-air missile. The annexed figure which forms a part of this specification shows schematically the bipropellant feed system and the motor of this missile. This same type of missile could be used as an air-to-air missile. This missile is suitable foroperations wherein the fuel and the oxidizer can be maintained at a tion delay, e.g., when using ammonium nitrate-containing H O, solution as the oxidizer and dimethylchlorodithioborate as the fuel, a temperature of about 70 F- In the drawing vessel 11 contains a quantity of gas at high pressure; this gas must be inert with respect to the oxidizer and the fuel; suitable gases are nitrogen and helium. Herein helium is used as the inert gas. Helium from vessel 11 is passed through line 12 and through valve 13 which regulates the flow of gas to maintain a constant pressure beyond valve 13. From valve 13 helium is passed through lines 14 and 16 into vessel 17 and simultaneously through line 18 into vessel 19.

Vessel 17 contains the oxidizer. Helium pressure forces the oxidizer out of vessel 17 through line 21 .to valve 22. Valve 22 is a solenoid actuated throttling valve. Suitable electrical lines connect valve 22 to an electrical source and operating switch (not shown) at the control chamber at the launching site. The oxidizer is passed through line 23 and injector 24 into combustion chamber 26. Combustion chamber 26 is provided with an outlet nozzle-27.

Vessel 19 contains the fuel. Vessels 17 and 19 are constructed to withstand the high pressure imposed by the helium gas. The gas pressure forces fuel from vessel 19 through line 28 to solenoid actuated throttling valve 29. Valve 29 is similar in construction and is actuation to valve 22. The fuel is passed through line 31 and injector 32 into combustion chamber 26.

Valves 22 and 29 are of such a size and setting that a predetermined ratio of oxidizer-to-fuel is passed into combustion chamber 26. Injectors 24 and 32 are so arranged that the streams of oxidizer and fuel converge and contact each other forcibly, resulting in a very thorough intermingling of the fuel and the oxidizer.

The missile is launched by activating the'solenoids on valves 22 and 29. In this example 4.5 volumes of oxidizer per volume of fuel is introduced into the combustion chamber. The oxidizer and the fuel react almost instantaneously upon contact in the combustion chamber; a large volume of very hot gas is produced in the combustion chamber, which gas escapes throughorifice 27. The reaction from this expulsion of gas drives, the missile toward its target.

1. A method of generating gas, which method comprises injecting separately and essentially simultaneously into the combustion chamber of a gas generator (1) a hypergolic fuel consisting essentially of a member selected from the class consisting of (i) organicdihalothioborates containing not more than 8 carbon atoms and (ii) diorganichalodithioborates containing not more than 12 carbon atoms and not more than 8 carbon atoms in an organic group, wherein the organic groups in (i) and (ii) above are aliphatic and the halogen radicals are selected from the class consisting of chlorine and bromine and Thus havin descr bed the invention, what is claimed (2) an oxidizer selected from the class consisting of (a) aqueous hydrogen peroxide solutions consisting of at least about 80 weight percent of H O; and the remainder essentially water and (11) aqueous hydrogen peroxide: ammonium nitrate solutions wherein the hydrogen peroxide-water portion is the predominant component and consists of at least about 80 weight percent of H and the remainder essentially water, in an amount and at a rate sufiicient to initiate a hypergolic reaction with and to support combustion of the fuel.

2. The method of claim 1 wherein said fuel is dimethylchlorodithioborate.

3. The method of claim 1 wherein said fuel is methyldichlorothioborate.

4. The method of claim 1 wherein said fuel is diethylchlorodithioborate.

5. The method of claim 1 wherein said fuel is ethyldii chlorothioborate.

6. The method of claim 1 wherein said oxidizer consists of about 80 weight percent of H 0 and the remainder essentially water.

7. The method of claim 1 wherein said oxidizer consists of about 90 weight percent of H 0 and the remainder essentially water.

8. The method of claim 1 wherein said oxidizer consists of a solution of hydrogen peroxide, water and ammonium nitrate, wherein the nitrate content is about 30 weight percent and the hydrogen peroxide-water portion consists of about 80 weight percent of H 0 and the remainder essentially water.

9. The method of claim 1 wherein said oxidizer consists of a solution of hydrogen peroxide, water and ammonium nitrate, wherein the nitrate content is about 40 weight percent and the hydrogen peroxide-water portion is the predominant component and consists of about 90 weight percent of H 0 and the remainder essentially water.

10. A method of generating gas, which method comprises injecting separately and essentially simultaneously into the combustion chamber of a gas generator (1) a hypergolic mixed fuel consisting essentially of (I) a liquid miscible hydrocarbon and (II) methyldichlorothioborate and (2) an oxidizer selected from the class consisting of (a) aqueous hydrogen peroxide solutions consisting of at least about 80 weight percent of H 0 and the remainder essentially water, and (b) aqueous hydrogen peroxide-ammonium nitrate solutions wherein the hydrogen peroxide-water portion is the predominant component and consists of at least about 80 weight percent of H 0 and the remainder essentially water, in an amount and at a rate sutficient to initiate a hypergolic reaction with and to support combustion of the mixed fuel.

11. The method of claim 10 wherein said hydrocarbon is a liquid petroleum fraction boiling between about 300 and about 600 F.

12. The method of claim 10 wherein said hydrocarbon isa liquid aromatic hydrocarbon boiling below about 600 F.

13. The method of claim 10 wherein said hydrocarbon is a liquid olefin boiling below about 600 F.

14. A method of generating gas, which method comprises injecting separately and essentially simultaneously into the combustion chamber of a gas generator (1) a hypergolic mixed fuel consisting essentially of (I) a liquid miscible hydrocarbon and (II) ethyldichlorothioborate and (2) an oxidizer selected from the class consisting of (a) aqueous hydrogen peroxide solutions consisting of at least about weight percent of H 0 and the remainder essentially water, and (b) aqueous hydrogen peroxide-ammonium nitrate solutions wherein the hydrogen peroxide-water portion is the predominant component and consists of at least about 80 weight percent of H 0 and the remainder essentially water, in an amount and at a rate sufiicient to initiate a hypergolic gelaftion with and to support combustion of the mixed 15. A method of gas generation, which method comprises injecting separately and essentially simultaneously into the combustion chamber of a gas generator (1) a hypergolic fuel consisting essentially of (A) trialkyltrithioborates wherein the alkyl groups contain from 1 to 3 carbon atoms and the total number of carbon atoms in the trithioborate is from 3 to 7 and (B) between about a trace and about 20 volume percent based on fuel of a halothioborate selected from the class consisting of (i) organic dihalothioborates containing not more than 8 carbon atoms and (ii) diorganichalodithioborates containing not more than 12 carbon atoms and not more than 8 carbon atoms in an organic group, wherein the organic groups in (i) and (ii) above are aliphatic and the halogen radicals are selected from the class consisting of chlorine and bromine and (2) an oxidizer selected from the class consisting of (a) aqueous hydrogen peroxide solutions consisting of at least about 80 weight percent of H 0 and the remainder essentially water and (11) aqueous hydrogen peroxide-ammonium nitrate solutions, wherein the hydrogen peroxide-water portion is the predominant component and consists of at least about 80 weight percent of H 0 and the remainder essentially water, in an amount and at a rate suflicient to initiate a hypergolic reaction with and to support combustion of the fuel.

16. The method of claim 15 wherein said halothioborate is methyldichlorothioborate.

17. The method of claim 15 wherein said halothioborate is ethyldichlorothioborate.

18. The method of claim 15 wherein said trithioborate is trimethyltrithioborate.

19. The method of claim 15 wherein said trithioborate is triethyltrithioborate.

20. The method of claim 15 wherein said halothioborate is present in the fuel in an amount between about 0.5 and 20 volume percent.

No references cited. 

1. A METHOD OF GENERATING GAS, WHICH METHOD COMPRISES INJECTING SEPARATELY AND ESSENTIALLY SIMULTANEOUSLY INTO THE COMBUSTION CHAMBER OF A GAS GENERATOR (1) A HYPERGOLIC FUEL CONSISTING ESSENTIALLY OF A MEMBER SELECTED FROM THE CLASS CONSISTING OF (I) ORGANICDIHALOTHIOBORATES CONTAINING NOT MORE THAN 8 CARBON ATOMS AND (II) DIORGANICHALODITHIOBORATES CONTAINING NOT MORE THAN 12 CARBON ATOMS AND NOT MORE THAN 8 CARBON ATOMS IN AN ORGANIC GROUP, WHEREIN THE ORGANIC GROUPS IN (I) AND (II) ABOVE ARE ALIPHATIC AND THE HALOGEN RADICALS ARE SELECTED FROM THE CLASS CONSISTING OF CHLORINE AND BROMINE AND (2) AN OXIDIZER SELECTED FROM THE CLASS CONSISTING OF (A) AQUEOUS HYDROGEN PEROXIDE SOLUTIONS CONSISTING OF AT LEAST ABOUT 80 WEIGHT PERCENT OF H2O2 AND THE REMAINDER ESSENTIALLY WATER AND (B) AQUEOUS HYDROGEN PEROXIDEAMMONIUM NITRATE SOLUTIONS WHEREIN THE HYDROGEN PEROXIDE-WATER PORTION IS THE PREDOMINANT COMPONENT AND CONSISTS OF AT LEAST ABOUT 80 WEIGHT PERCENT OF H2O2 AND THE REMAINDER ESSENTIALLY WATER, IN AN AMOUNT AND AT A RATE SUFFICIENT TO INITIATE A HYPERGOLIC REACTION WITH AND TO SUPPORT COMBUSTION OF THE FUEL. 